xvil CHARACTERS OF LEMURS 535 second toe is furnished with a sharp nail, unlike the flattened nails of the other fingers and toes, and in Tarsiits the third also is thus provided. As to osteology, the shape of the head, already referred to, indicates some of the differences in the skull which mark off the JL.em.urs from, the Anthropoidea. The brain case is small relatively to the face; the orbital and temporal fossae are in communication, though the frontal and jugal bones are united behind the orbit. The two halves of the lower jaw are not in- variably ossified to form one piece, as is the case with most Apes. The lachrymal foramen lies upon the face in front of the orbit. The teeth are characteristic; not so much in their number (the dental formula is usually I 2, C 1, Pm 3, M 3 =* 36) as in the disposition of the incisors. The incisors of the lower jaw and the canines project forwards in a way only found in a few American Monkeys ; as in the Apes there are four incisors in each jaw, but, with the exception of the highly aberrant ChiTowiys, there is a space in the upper jaw between the incisors of the two sides. The canines of the lower jaw, moreover, are often incisiform. There is a well-developed sublingua beneath the tongue (see p. 61). The stomach is perfectly simple ; and the caecum, always present and varying in length, never has a vermiform appendix. The gall-bladder is always present. The brain differs from that of the Anthropoidea in that the cerebellum is* as in the lower Mammalia, exposed. The convolutions upon the cerebral hemi- spheres are not greatly developed, a circumstance, however, which. (see pr 7*7) may have more relation to the size of the animals than to their mental development. Though the "brain in its general outlines is not like that of the other Primates, there are certain resemblances; the most striking of these is perhaps the presence, though in rather a rudimentary condition, of the te Simian fissure." The Lemurine brain has been chiefly studied by Slower/ by Milne-Edwards,2 and by myself.8 There are also a number of scattered papers dealing with particular types, such as the memoirs of Owen4 and Oudemans,5 upon the brain (and the general anatomy) of Chiromys. Without going into great * Trans. Zool. S&c. v. 1863, p. 103. 2 Hist. Wat. de Madagascar^ Mamm, 1875. s PTOG. Zool. Soc, 1895, p. 142. * Trans. Zool. Sac. v. 1863, p. 33. 6 Petft. Ak. Amsterdam, xx.vii. 1890, Art. 2.